Today, within the pulp and paper industry, there is a more frequent closing of the white water systems. This is, as such, a positive environmental factor, by reducing the discharge to different recipients, but means increased problems, as well, within the industry by accumulation of different compounds in the white water systems as closed. Thus there is an accumulation of resins and heavy metals in the white water, which different compounds have to be eliminated in order not to create problems at the production of paper and pulp at the renewed use of the white water. Resins and heavy metals are present in different concentrations in the wooden raw materials depending on its origin.
The resins can be precipitated chemically by using flocculation agents followed by flotation or sedimentation whereby the white water as such can be treated using such a flocculating agent.
One has, however, not known how to treat the heavy metals.